Development

Landscape changes that replace semi-natural habitats such as woodland and farmland with urban environments dominated by buildings, roads and other man-made infrastructure (such as wind turbines) have the potential to affect bat populations in a number of ways, both directly through habitat loss or fragmentation or indirectly through secondary impacts such as lighting.

Urbanisation

Some bat species in the UK make use of urban habitats. For example, in a study of habitat use of bats (predominantly pipistrelle species) across the UK, urban habitats were positively selected in some land classes and used according to availability in others (Walsh & Harris 1996); Leisler’s bat was shown to use urban habitats and forage along roadsides in a study in Kent (Waters et al. 1999) and common pipistrelles are regularly found in urban habitats (e.g. Wicht et al. 2003). However data from the National Bat Monitoring Programme was used to show that common pipistrelles demonstrate a strong negative response to local urbanisation (within 1km), despite the fact that it is thought to be well adapted to the urban landscape (Lintott et al. 2016). A study in Birmingham, UK, examined bat activity around urban ponds, along an urban-rural gradient and showed that most bat species studied demonstrated a negative association with urbanisation (Hale et al. 2012). However, common pipistrelle displayed a nonlinear relationship between activity and built area. Activity was highest at around 40% built land-cover but rapidly reduced as built land-cover increased above 60%, leading the authors to propose that this may represent a threshold or tipping point.

Loss of roosts

A fundamental ecological requirement for all bat species is the use of roosts (safe resting places which play many different roles in the bat life-cycle). Bats need suitable roosting locations within commuting distance of foraging habitat and most species make use of several different types of roost during the year to meet different biological and energetic needs. Many different natural and man-made structures may be used as roosts by bats. Examples of man-made structures that are used as roosts in Europe include houses, castles, churches, bridges, blocks of flats, barns and stables (Marnell & Presetnik 2010) and at least 13 of the 17 bat species that are resident in the UK are known to use built structures for roosts. Within Europe all bat roosts have legal protection from damage or destruction.

While little is published on the extent to which roost availability may limit the distribution or abundance of bats, the loss of roosts was one of the factors implicated in late twentieth century population declines (Racey & Stebbings 1972, Stebbings 1995). Renovation of or refitting existing buildings and the conversion of buildings such as barns to new uses may often result in them becoming less suitable as bat roosts. Some species, for example Natterer’s bat and brown long-eared bat, are considered to be especially vulnerable to such changes, because they have quite specific roosting requirements which may not be present after buildings have been altered. Recent changes in building practices to enhance energy efficiency are a new concern, since these buildings may offer few opportunities for use by bats and other wildlife (Mitchell-Jones 2010).

The loss of natural roosts has also been a serious issue in the past, and remains an ongoing risk. The widespread loss of cave and underground hibernation sites through destruction, blocking and gating of entrances is considered to have contributed to past population declines (Stebbings 1995). Roosts in trees are vulnerable to management practices that selectively remove important potential roosting sites such as standing deadwood or trees that have woodpecker holes.